A Chinese Foreign Ministry spokesman refuted groundless criticisms on China's national defense policy made by a newly-released Japan's annual defense white paper, urging the country for serious introspection.

"China strongly opposes to the groundless criticisms on China's normal national defense development and military activities, and the irresponsible remarks on China's internal affairs made by Japan's annual defense white paper," spokesman Hong Lei said in a written statement released Tuesday in Beijing.

According to Hong, China has already made solemn representations with Japan on that matter.

Hong also noted that Japan has caught wide attention from regional and international communities by making various excuses for its continuous arms expansion, reinforcement of military alliance and distorting facts on regional security issues in recent years.

"What is Japan's real motivation by doing so?" Hong asked.

The spokesman also urged Japan to seriously re-examine itself and introspect whether such actions could be conducive to the regional peace and stability.

Japan on Tuesday released its annual Defense of Japan report, expressing concern over Chinese naval vessels' activities in the Pacific Ocean.

The report noted that China is likely to expand its sphere of maritime activities, and conduct operations and training as routine practices in waters near Japan including the East China Sea, the Pacific Ocean, and the South China Sea, which Tokyo is increasingly worried about.